The United States reported 109 laboratory-confirmed cases, including one death, and Mexico, ground zero for the outbreak, reported 97 confirmed cases of infection, including seven deaths. Mexican health officials said they believe the virus is responsible for more than 150 deaths and more than 2,000 illnesses.

WHO broke down the lab-confirmed cases with no deaths as: Canada, 19; Spain, 13; Britain, eight; Germany and New Zealand, three each; Israel, two; and the Netherlands, Austria and Switzerland, one each.

People in Mexico braced for a five-day shutdown of offices, restaurants, schools and soccer stadiums beginning Friday. In a televised speech Wednesday, Mexican President Felipe Calderon said the shutdown would last until at least Tuesday.

The entire Fort Worth, Texas, school district shut down until at least May 8 after health officials reported four probable cases of swine flu among the district's 80,000 students.

Several Asian countries implemented their pandemic plans, including stepped-up border surveillance, after WHO raised its alert level.

Officials at the Centers for Disease Control in Atlanta said they think the number of confirmed U.S. cases will increase as labs complete testing on cases now termed "likely" or "probable," The New York Times reported.

During a Senate subcommittee hearing this week on U.S. preparedness, Paul Jarris, executive director of the Association of State and Territorial Health Officials, urged senators to spend more than $1 billion to help states respond to a potential pandemic, Stateline.org reported Thursday. He said federal funding cuts and layoffs of healthcare professionals because of the recession could hamper states' ability to respond to a pandemic.

Reports of swine flu cases appeared in locations such as Peru, Switzerland and Japan, the Times said.

In China, the state-run Xinhua news agency reported Vice Premier Li Keqiang toured the Chinese Center for Disease Control and Prevention in Beijing Wednesday and called on manufacturers to produce more face masks, sterilization chemicals and flu medicines.